Cartridge seal

ABSTRACT

A seal cartridge for providing a fluid seal between a rotating shaft and a housing such as found in a centrifugal pump. The seal cartridge includes rotating and non-rotating seal portions. The non-rotating seal portion includes a seal ring seat that is connected to the support sleeve by a frangible element. During installation, the frangible element is separated to release the non-rotating portion of the seal from the support member. The non-rotation seal portion includes an O-ring held by a stationary seal holder. An O-ring seal seals a circumferential periphery of the seal ring to inhibit fluid leakage between the holder and the seal ring. An inside radial end face of the seal ring abuttingly engages a radial end face defined by the holder which enhances heat transfer between the seal ring and the holder. A plurality of grooves or recesses are formed in either the inside end face of the seal ring or the radial end face of the holder and are arranged to receive cooling fluid from the pump housing to further promote cooling of the seal.

TECHNICAL FIELD

The present invention relates generally to rotary, mechanical shaftseals and in particular to an improved cartridge seal.

BACKGROUND ART

Pumps and similar equipment which include rotating shafts have beenprovided with seals of various types to prevent leakage along theirshafts. One conventional type of seal is known as a face seal andtypically comprises a rotating portion fixed to the shaft defining aradial sealing face and a fixed portion secured to the housing alsodefining a radial sealing face, the two sealing faces disposed inabutting, sealing contact. Normally, the seal faces are maintained inengagement by a spring forming part of the seal assembly.

Examples of this type of seal can be found in U.S. Pat. No. 3,447,810and U.S. Pat. No. 4,342,538, both owned by the assignee of the presentapplication.

U.S. Pat. No. 4,815,747 discloses a cartridge form of a pump seal thatis used to seal the pump shaft of a centrifugal pump. All the sealsdisclosed in the above-referenced U.S. patents, include non-rotatingseal sections mounted in a pump cavity and a rotating seal sectionmounted to the shaft. The rotating seal section includes a coil springsurrounding the shaft for spring loading a rotating seal ring towardsengagement with a non-rotating seal ring forming part of the fixed sealsection. Both seal rings define radial faces which during pump operationsealingly engage.

In the seal construction disclosed in the '810 and '538 patents, therotating and non-rotating seal sections are separately installed intothe pump. In the '747 patent, the non-rotating and rotating sealsections are in a cartridge form prior to installation. Duringinstallation, a frangible element separates so that the rotating sectioncan rotate with a pump shaft whereas the non-rotating section is fixedto the pump housing. The cartridge seal disclosed in the '747 patent hasenjoyed great commercial success.

DISCLOSURE OF THE INVENTION

The present invention provides a new and improved seal cartridge forsealing the interface between a rotating shaft and a stationary housingsuch as that found in a centrifugal pump. The cartridge seal of thepresent invention represents an improvement in the cartridge sealdisclosed in U.S. Pat. No. 4,815,747, which is hereby incorporated byreference. According to the invention, the seal cartridge is constructedas a unitary assembly having interconnected rotating and non-rotatingportions. During installation of the seal cartridge, the couplingbetween the rotating and non-rotating portions is disconnected orseparated so that after installation, the rotating portion isoperatively connected to the shaft and the non-rotating portion is fixedto the housing. A rotating, sealing interface is defined between thenon-rotating and rotating portions.

To facilitate the explanation of the invention, it will be described inconnection with its use in a centrifugal pump. It should be understood,however, that the invention can be used in any application that requiresa rotary seal for sealing a shaft/housing interface.

In the preferred embodiment, the seal cartridge includes a supportmember which prior to installation supports both the non-rotating androtating portions of the seal. According to the invention, a frangiblemember couples the non-rotating portion of the seal to the supportmember.

The rotating seal portion is the same or similar to the rotating sealportion disclosed in the '747 patent. The non-rotating portion of theseal includes a seal holder or seal seat which supports a stationaryseal ring. The holder is sealingly received by pump housing structure.In the preferred and illustrated embodiment, a peripheral seal surroundsthe stationary seal ring and sealingly engages an axial inside surfaceof the holder. The O-ring may be carried by a groove in the stationaryseal ring located intermediate inside and outside end faces of the sealring. Alternately, the groove may be an end groove located on the insideface of the seal ring. In still another alternative, the O-ring may becarried by an internal groove formed in the holder or stationary seat.

The non-rotating portion of the seal includes a seal seat or holderwhich supports the stationary seal ring and which is secured to housingstructure. According to a feature of the invention, the stationary sealring includes an inside end face which confrontingly engages a radialsurface or radial face of the stationary holder. The abutting engagementbetween the seal ring and the holder promotes heat transfer from theseal ring to the holder from where it is transferred to the pumphousing. With the present invention, cooling of the seal is promotedresulting in increased seal life.

According to the invention, the seal cartridge is installed into themechanism i.e. pump, by placing the assembly onto the shaft. The supportmember is pushed or advanced until the seal seat reaches its installedposition. Further advancement of the support member causes the frangiblecoupling to separate so that the non-rotating portion of the seal isdecoupled from the support member enabling the rotating portion torotate relative to the non-rotating portion.

In the preferred embodiment, the support sleeve is advanced onto theshaft until an end surface abuts a shoulder formed on the shaft. Thesleeve is locked or clamped in position by a locking element which locksthe support sleeve and hence the rotating portion of the seal to theshaft.

In the disclosed embodiment, the seal cartridge is used to seal therotating shaft of a centrifugal pump. In this embodiment, the seal islocated in a seal cavity defined by a cup-shaped seal plate. The pumpshaft includes a threaded end adapted to threadedly receive an impeller.In the preferred installation method, the seal cartridge is placed onthe end of the impeller shaft and the impeller is then threaded onto theshaft end. An inner end-face of the impeller abuts an end of the sealcartridge and advances the support sleeve axially along the pump shaftas the impeller is threaded onto the shaft end. The support sleeve issized such that when fully installed, it is clamped between the innerend-face of the impeller and a shoulder formed on the pump shaft and isrigidly held thereto.

According to additional features of the invention, the stationary sealring and/or seal ring holder includes a plurality of slots for receivinglubricating fluid from inside the pump housing. The slots may be formedon an inside end face of the seal ring so that when the seal ringabuttingly engages the radial surface on the holder, cooling oil isreceived in the region where heat transfer between the seal ring and theholder occurs. Alternately, the slots may be formed in the radial heatexchange surface of the holder.

Additional features of the invention will become apparent and a fullerunderstanding obtained by reading the following detailed descriptionmade in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features of the present invention will becomeapparent to one skilled in the art to which the present inventionrelates upon consideration of the following description of the inventionwith reference to the accompanying drawings, wherein:

FIG. 1 is a fragmentary, sectional view of a centrifugal pump showing aseal cartridge, constructed in accordance with a preferred embodiment ofthe invention, as it appears at the beginning of an installationprocess;

FIG. 2 is another fragmentary, sectional view of the centrifugal pumpshowing the seal cartridge as it appears at the completion of theinstallation process;

FIG. 3 is an exploded view of the cartridge seal constructed inaccordance with the preferred embodiment of the invention and a pumpshaft;

FIG. 4 is an enlarged, fragmentary sectional view of the cartridge sealshown in FIG. 2;

FIG. 5 is a fragmentary, sectional view of an alternate embodiment ofthe cartridge seal;

FIG. 6 is a fragmentary, sectional view of another embodiment of thecartridge seal;

FIGS. 7A and 7B illustrate a seal ring construction that includescooling slots, constructed in accordance with a preferred embodiment ofthe invention;

FIGS. 8A and 8B illustrate another embodiment showing cooling slots inan alternate seal ring; and

FIGS. 9A and 9B illustrate a seal ring holder constructed in accordancewith a preferred embodiment of the invention that includes coolingslots.

BEST MODE FOR CARRYING OUT THE INVENTION

FIGS. 1 and 2 illustrate the overall construction of a seal cartridge10, constructed in accordance with the preferred embodiment of theinvention, shown as it appears at the commencement of an installationprocess (FIG. 1) and as it appears after the installation process iscompleted (FIG. 2).

Turning first to FIGS. 1 and 2, the seal cartridge 10 is shown as itwould be used in a pump application. In particular, the seal 10 isoperative to seal the interface between a pump shaft 12 and a pumphousing (a portion of which is indicated generally by the referencecharacter 14) to inhibit fluid leakage along the shaft and into theinterior of the housing 14. In the disclosed embodiment, the pump is ofthe centrifugal type and includes an impeller 16 threadedly mounted to athreaded end 12 a of the pump shaft 12. The impeller 16 includes athreaded central bore 17 for receiving the shaft end 12 a.

The housing 14 defines a cup-shaped seal cavity 18 including a machinedrecess 18 a which receives a non-rotating portion 10 a of the cartridgeseal 10. The remainder of the seal cavity 18 shrouds a rotating part 10b of the cartridge seal and at least partially protects seal componentsfrom-material being pumped through an impeller chamber (not specificallyshown, but indicated generally by the reference character 20.

According to the invention, the seal cartridge 10 is constructed as aunitary assembly with the rotating portion 10 b and the non-rotatingportion 10 a coupled together so that both portions of the seal areinstalled concurrently during an installation process.

With the illustrated construction, the entire seal 10 including both therotating and non-rotating portions 10 a, 10 b are installedconcurrently. The alignment of the parts are maintained throughout theinstallation process.

The present invention represents an improvement over a cartridge sealdisclosed in U.S. Pat. No. 4,815,747, owned by the Assignee of thepresent application, and is hereby incorporated by reference. The sealcartridge disclosed in the '747 patent illustrates and providesadditional details regarding a cartridge seal having rotating andnon-rotation portions that are coupled together prior to installation sothat both portions of the seal are installed concurrently. During theinstallation process, and as more fully described in the '747 patent,the coupling between the rotating and non-rotating portion is broken.

Referring also to FIG. 3, the seal cartridge 10 includes a tubularsupport member 30 which is adapted to fit around or receive the pumpshaft 12. The support member 30 includes an O-ring type seal 32 forinhibiting fluid leakage between itself and the pump shaft 12. A leftend 30 a of the support member 30 (as viewed in FIG. 1) mounts acentering washer 34 which also serves as a spring seat for a biasingspring 36. A frangible mounting ring 38 is carried near a right end 30 b(as view in FIG. 3) of the support member 30 which, at least for aportion of the installation process, rigidly supports a non-rotatingseal ring seat or holder 40 which forms part of the non-rotating portion10 a of the cartridge seal 10. The frangible ring 38 causes the sealring seat or holder 40 to move with the support member 30 as the supportmember is advanced along the pump shaft 12 i.e. towards the right asviewed in FIG. 1.

The non-rotating seal ring seat 40 includes an O-ring seal 42 whichsealing engages the recess 18 a to inhibit fluid leakage between itselfand the housing 14. The stationary seal ring holder 40 carries a sealring or face seal element 22 b in a way that inhibits relative rotationbetween itself and the seal ring 22 b and also carries an O-ring seal 44for inhibiting fluid leakage between the seat 40 and the seal ring 22 b.

According to the invention, the circumferential, O-ring seal 44, sealsthe periphery of the seal ring 22 b to an inside, axial surface 40 a ofthe holder 40. In the embodiment illustrated in FIG. 1-3, the peripheralO-ring 44 is carried in an O-ring groove defined by the seal ring 22 b.A peripheral seal comprising an O-ring carried in an internal grooveformed in the holder 40 is also contemplated.

As seen best in FIGS. 1 and 2, according to a feature of the invention,an inside, radial end surface 66 defined by the seal ring 22 b directlyabuts a radial end surface 40 b defined by the holder 40. The abuttingengagement between these two surfaces 66, 40 b promotes heat transferfrom the stationary seal ring 22 b and the holder 40 and, in turn, istransferred to the housing 14 for dissipation. It has been found, thatwith the disclosed construction, the life of the seal rings 22 a, 22 bare increased since the transfer of heat away from the interface betweenthe non-rotating seal ring 22 b and a rotating seal ring or face seal 22a is facilitated.

It should also be noted here that in the illustrated embodiment, thefrictional engagement of the O-ring seal 42 with the housing recess 18 aand the holder 40 inhibits relative rotation between these components.Similarly, the O-ring seal 44 inhibits relative rotation between theholder 40 and the face seal 22 b. Mechanical engagement structure suchas splines, lugs, pins, etc. between the holder 40 and the housing 14and/or the holder 40 and the sealing element 22 b are also contemplatedby the invention.

As is conventional, the rotating portion 10 b of the seal cartridge 10includes a bellows member 46 clamped at its left end to the supportmember 30 (as viewed in FIG. 1) by a drive band 47. Referring also toFIG. 4, the transmission of torque from the drive shaft 12 to therotating seal ring 22 a is achieved as follows. The right end of thebellows 46 is connected to the rotating seal ring 22 a and allows theseal ring 22 a to move axially towards and away from the stationary sealring 22 b. A conventional cage member 48 supports the seal ring 22 a androtatably couples the ring to the bellow 46 and, hence the supportmember 30, while allowing axial movement in the seal ring 22 a relativeto the support member 30. Splines or lugs/lug engaging recesses (notshown) may be formed on the cage (and on the seal ring 22 a) to providethe requisite drive coupling between the elements. The drive band 47includes a plurality of axially extending tabs that are received inassociated slots (not shown) formed in the cage 48. The engagementbetween the slots and the tabs provide a slidable coupling between thecage 48 and the drive band 47 (and hence the bellows 46). The biasingspring 36 acts between the centering washer 34 and a lip 48 a of thecage 48 and exerts a biasing force on the seal ring 22 a urging a radialface 50 into abutting, sealing contact with a radial face 52 of the sealring 22 b. The elements 47, 46, 48 and the method by which the seal ring22 a is coupled to the drive shaft 12 is considered conventional.Additional details can be found in the '747 patent. As more fullydescribed in U.S. Pat. No. 4,815,747, the drive band or other retainingstructure causes the bellows member 46 to frictionally engage thesupport member 30. The frictional engagement enables the bellows toslide axially along the support member during installation if sufficientforce is applied. During pump operation the bellows member 46 grips thesupport member with a frictional force sufficient to transmit torque toa rotating seal ring or face seal 22 a when the shaft 12 rotates.

As indicated above, at the commencement of the installation process, therotating and non-rotating portions 10 b, 10 a of the seal cartridge 10are interconnected so that both portions are installed concurrently. Inparticular, the stationary seal ring seat 40 is coupled to the supportmember 30 by the frangible ring-like element 38. For purposes ofexplanation the element 38 will be termed a “shear ring”. As seen bestin FIG. 3, the shear ring 38 is carried by an annular groove 60 formednear the right end 30 b of support member 30 (as viewed in FIG. 1).Further details of the shear ring and its function can be found in U.S.Pat. No. 4,814,747.

In the preferred installation method and referring in particular toFIGS. 1 and 2, the cartridge assembly 10 (including cross-coupledrotating and non-rotating portions 10 b, 10 a) is placed on the pumpshaft 12. The bore 78 of the support member 30 is sized to receive thepump shaft 12, preferably with a fairly close fit. The pump impeller 16is then threaded onto the end 12 a of pump shaft 12 which is then usedto press the seal cartridge 10 into position. As the pump impeller 16 isthreaded onto the pump shaft 12, a radial face 16 a engages a radial endface 88 defined by the left end 30 a of the support member 30. A shim 89may be placed between the faces 16 a, 88. Rotation of the impeller ontothe shaft 12 and pushes the support member 30 towards the right (asviewed in FIG. 1). i.e. towards its installed position (shown in FIG.2). The shear ring 38 supports the non-rotating seal ring seat andmaintains its alignment with the seal cavity recess 18 a. In thepreferred installation method, the support member 30 is gradually pushedaxially along the shaft 12 and carries or drives the seal ring seat 40into the housing recess 18 a.

After the seal ring seat 40 bottoms in the recess 18 a i.e. once anouter radial end face 40 c of the seat abuts a radial end surface 90defined by the recess 18 a, continued advancement of the support member30 (by rotating the impeller further onto the pump shaft 12) causes tabportions 38 a of the shear ring 38 to separate from an annular band-likeportion 38 b as seen in FIG. 4. The tabs sever or fracture in theregions of weakness defined by the shear ring. The support member 30advances axially along the pump shaft 12 until a right end (as viewed inFIG. 2) abuts a shoulder 92 formed on the pump shaft. The frictionalengagement between the support member 30 and the bellows 46 forms atorsionally strong bond for transmitting torque from the shaft 12 to theseal ring 22 a.

The support member 30 is locked to the pump shaft 12 by virtue of beingclamped between the radial face 16 a of the impeller 16 and the shoulder92 on the pump shaft 12. After installation, the non-rotating androtating portions 10 a, 10 b of the seal are relatively rotatable. Thefluid seal is established by the abutting contact between the radialseal faces 50, 52 defined by the rotating and non-rotating seal rings 22a, 22 b, respectively (shown in FIG. 4). With the disclosed invention, arotary shaft seal on a pump or other mechanism can be easily replaced inthe field even in those situations where space or access to the sealregion is limited. With the disclosed invention, seal installation is aone step process and eliminates the need for separately installing afixed, non-rotating seal ring seat into the housing followed by theinstallation of a rotating seal portion onto the shaft.

FIG. 4 is an enlarged sectional view of the cartridge seal 10 shown inFIGS. 1-3. It should be noted that the O-ring seal 44 is carried in anO-ring groove 68 formed in the non-rotating seal face 22 b. The O-ringgroove 68 is generally located centrally on the periphery of the sealring 22 b. FIG. 4 also illustrates the condition of the shear ring 38after installation. As described above, it is a frangible ring thatsplits into two parts 38 a, 38 b during installation.

FIG. 5 illustrates an alternative construction for the cartridge seal10′. In this alternate embodiment, an O-ring 44′ which serves the samepurpose as the O-ring 44 shown in FIG. 4, is carried by an O-ring groove68′ that is formed in the stationary seal holder 40′. The seal 22 b′does not have an O-ring groove.

FIG. 6 illustrates another alternative embodiment. In this embodiment,an O-ring seal 44″ for sealing a seal ring 22 b″ to the holder 40 iscarried in an end groove 68″ formed in the face seal 22 b″. In thepreferred embodiment, the axial length of the groove 68″ is wider thanthe diameter of the O-ring 44″ so that after installation, the O-ring44″ does not exert an axial force on the holder surface 40 b. It onlyexerts a sealing engagement with the axial surface 40 a of the holder40.

The term “O-ring” used above is intended to serve as a genericdescription for an annular type seal. This invention is not limited toan “O-ring” having a circular cross section. “O-rings” with rectangular(often termed quad rings), oblong and other cross sections arecontemplated by the present invention.

As viewed in FIGS. 1 and 2, the region of the pump indicated generallyby the reference character 70 is a bearing housing that is filled withlubrication oil or coolant fluid. As a result, a right end face 40 c ofthe holder 40 is in contact with and is bathed in oil, (including shaft12). According to the invention, alternate constructions for both theseat 22 b and the holder 40 are contemplated to promote further coolingof these components by the lubricating oil in the chamber 70.

FIGS. 7A and 7B illustrate one alternate embodiment. In this embodiment,the relationship between the stationary face seal 22 b″′ and thestationary holder 40 is similar to that shown in FIG. 4, i.e., theO-ring seal 44 is carried in the O-ring groove 68 formed in the sealring 22 b″′. However, in this alternate construction, the seal ring 22b″′ is formed with a plurality of radial cooling slots 80 that receiveoil from the pump chamber 70. This lubricating oil communicated betweenthe seal ring 22 b″′ and the end face 40 b of the holder 40 promotecooling of those components. In addition, the same type of face sealring 22 b″′ with the radial slots 80 can be used with the constructionshown in FIG. 5, i.e., with the O-ring seal 44′ carried in an O-ringgroove 68′ formed in the holder 40′.

FIGS. 8A and 8B illustrate a method and apparatus for increasing thecooling for the alternate construction shown in FIG. 6. In thisalternate construction, a stationary face seal 22 b″″ (which includesthe end groove 68″ for carrying the O-ring seal 44″) includes aplurality of radial slots 80′ for receiving lubricating oil from thechamber 70. The addition of this lubricating oil to the slot regionspromotes cooling of the stationary face seal 22 b″″ and the holder 40.

FIGS. 9A and 9B illustrate another alternate construction which includescooling of seat holder 40″ and face seal 22 b. The construction shown inFIGS. 9A, 9B is similar to that shown in FIG. 4 in that the O-ring seal44 is held in an O-ring groove 68 formed in the face seal 22 b. However,in this alternate construction, a modified seal holder 40″ is disclosedwhich includes a plurality of radial slots 90 formed in the radialendface 40 b of the alternate holder 40′. Like the slots 80 shown inFIGS. 8A and 8B, the slots 90 receive lubricating oil or fluid from thepump chamber 70 and promote cooling of the holder 40″ and/or the faceseal or seal ring 22 b.

The stationary seat 40″ including the radial slots 90 can also be usedin the alternate construction shown in FIGS. 5 and 6. However, theradial slots 90 would be reduced in length for the configuration shownin FIG. 6, so that the lubricating oil from the bearing chamber 70 isnot communicated to the end groove 68″. In other words, the radialextent of the slots 90 would stop short of the end groove 68″.

Although the invention has been described with a certain degree ofparticularity, it should be understood that those skilled in the art canmake various changes to it without departing from the spirit or scope ofthe invention as hereinafter claimed.

1. A seal cartridge for providing a fluid seal between a rotating shaftand a housing, comprising: (a) a tubular support member adapted toreceive a rotatable shaft; (b) said support member supporting rotatingand non-rotating seal portions, said rotating portion being coupleableto a rotatable shaft and said non-rotating portion being coupleable to ahousing; (c) a frangible support means for supporting said non-rotatingseal portion in a predetermined position with respect to said rotatingportion, during an installation process; and, (d) said non-rotatingportion including: (i) a stationary holder defining an inside axialsurface and an inside radial surface; (ii) a stationary seal ring heldby said holder, said seal ring defining an inside radial surfaceabuttingly engageable with said inside radial surface defined by saidholder, said abutting engagement permitting heat transfer between saidseal ring and said holder; and (iii) an O-ring seal engageable by acircumferential peripheral surface defined by said seal ring and saidinside axial surface of said holder whereby fluid flow between said sealring and said holder is inhibited.
 2. The apparatus of claim 1 whereinsaid O-ring is carried in a groove defined by said seal ring.
 3. Theapparatus of claim 2 wherein said groove is located intermediate saidinside end face and an outside sealing face defined by said seal ring.4. The apparatus of claim 2 wherein said groove is an end groove locatedon said inside end face of said seal ring.
 5. The apparatus of claim 1wherein said O-ring is carried in a groove defined by said holder. 6.The apparatus of claim 1 wherein said seal ring includes a plurality ofrecesses for receiving cooling fluid.
 7. The apparatus of claim 1wherein said inside radial face of said holder includes a plurality ofrecesses for receiving cooling fluid.
 8. The apparatus of claim 6wherein said recesses are radially directed slots.
 9. The apparatus ofclaim 7 wherein said recesses are radially directed slots.
 10. Acartridge seal for sealing a pump shaft of a pump, comprising: a) arotating section including a rotatable seal ring adapted to rotate withsaid pump shaft; b) a non-rotating section sealingly engageable withnon-rotating pump structure of said pump, said non-rotating sectionincluding a non-rotating seal ring held by a non-rotating seal holder;c) an O-ring for sealing an axial, peripheral surface of said seal ring,to said holder; and d) said holder defining an inside radial end faceabuttingly engageable by an inside end face of said seal ring wherebysaid seal holder and said seal ring are in a heat transfer relationship.11. The apparatus of claim 10 wherein said O-ring is carried in a groovedefined in said seal ring.
 12. The apparatus of claim 10 wherein saidinside end face of said seal ring includes a plurality of recesses forreceiving a cooling fluid.
 13. The apparatus of claim 10 wherein saidinside radial surface of said holder includes a plurality of recessesfor receiving a cooling fluid.
 14. The apparatus of claim 12 whereinsaid cooling fluid is lubricating oil contained in a bearing chamberdefined by said pump.
 15. The apparatus of claim 13 wherein said coolingfluid is lubricating oil contained in a bearing chamber forming part ofsaid pump.
 16. The apparatus of claim 10 wherein said O-ring is carriedin a groove defined in said holder.